In the automotive industry, there has been ongoing research on improvement of emissions. For minimizing hydrocarbons (HO) in evaporation gas of gasoline fuel, emissions from fuel evaporation have been reduced to under 0.5 g/day in some countries, and it will be further limited to under 0.054 g/day by law.
Improvements in fuel tank materials and optimizing connection structures have been further studied in order to minimize generation of fuel evaporation gas that permeate from the fuel tank, and a fuel vapor recirculation device provided with a canister has also been used.
The canister contains an absorbent material such as activated carbon for absorbing the fuel vapor or fuel evaporation gas from the fuel tank, or a float chamber for preventing discharge of the fuel vapor or fuel evaporation gas to the atmosphere.
The absorbed fuel vapor can be transmitted to an engine for combustion through a pressure control solenoid valve (Purge Control Solenoid Valve; PCSV) that is controlled by an engine control unit (ECU).
The fuel vapor purge system supplies fuel vapor collected in the canister to an intake manifold or an intake line at a front end of a compressor of a turbocharger by using a positive pressure and a negative pressure formed in the intake manifold, and then the fuel vapor is supplied to a combustion chamber of the engine.
However, in case of a hybrid vehicle which has been recently researched and developed, a negative pressure is frequently not generated in the intake manifold. For example, in case of a hybrid vehicle, the vehicle is driven by operation of a motor in many cases, and when an idle stop-and-go (ISG) system is installed, the operation of the engine is periodically stopped. Further, when a turbocharger operates, fuel vapor cannot be purged often due to an excessive pressure supplied to the intake manifold.
As described, since the negative pressure is not frequently generated in the intake manifold in case of the hybrid vehicle which has been recently researched and developed, a problem that it cannot cope with the regulations of the fuel vapor evaporated in a fuel tank arises.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.